Glow plug

ABSTRACT

A combustible vapor ignition device in the form of an elongated plug having a threaded body end and a coaxially disposed center electrode disposed in but spaced from an elongated bore through the body of the plug, the electrode being electrically insulated by insulation material from the body but electrically connected thereto only through a glow element disposed in the bore and attached between the inner end of the electrode and the lower end of the body, the electrode including an increased diameter electrode portion disposed in an increased diameter bore portion of the elongated bore, an annular spring washer being disposed about the center electrode between either the upper or lower wall of the increased diameter bore portion and the increased diameter electrode portion to exert a constant compression force therebetween to permanently prevent gas under pressure located in the lower portion of the bore from passing about the increased diameter electrode portion to the upper portion of the bore.

United States Patent 11 1 [111 3,91 1,326 Ohlsson Oct. 7, 1975 GLOW PLUG Primary Examiner-Volodymyr Y. Mayewsky [76] Inventor: Irwin G. Ohlsson, 27437 Eastvale Attorney Agent or Flrm lohn Holmchter Road,'Rolling Hills, Calif. 90274 22 Filed: Mar. 10, 1975 [57] ABSTRACT A combustible vapor ignition device in the form of an [21] Appl' 556734 elongated plug having a threaded body end and a coaxially disposed center electrode disposed in but [52] U.S. C1. 317/98; 123/145 A; 219/217; sp ed from an elongated bore through the body of 432/262 the plug, the electrode being electrically insulated by [51] Int. Cl. F23Q 7/10 insulation material from the body but electrically con- [58] Field of Search 219/267, 270; 317/79, 98; nected thereto only through a glow element disposed 431/262; 123/145 A in the bore and attached between the inner end of the electrode and the lower end of the body, the electrode [56] Referen e Cited including an increased diameter electrode portion dis- UNITED STATES PATENTS posed in an increased diameter bore portion of the 2,129,962 9/1938 Rabezzana 123/145 A x elongated bore an annullar Sprngbwasher 5? 5" 2140,943 12/1938 Rudguist 123/145 A pose about the center eectfo e t e 2404 841 7/1946 Hess etal. 317/98 upper or lower wall of the mcreased bore 2:482:83! 9/1949 Arden .4 123/145 A portion and the increased diameter electrode portion 2,484,544 10 1949 B nn et a], 2 270 to exert a constant compression force therebetween to 2,492,755 12/1949 McCollum 317/98 permanently prevent gas under pressure located in the 2,500,395 3/l950 Arden 123/145 A lower portion of the bore from passing about the in- 3,0l7,54l Lawser creased diameter eectrode portion to the upper p01- 3,044,458 7/1962 Finvik 123 145 A tion ofthe bore. 3,434,012 3/1969 Rademacher 317/98 10 Claims, 5 Drawing Figures 4 1 l I l, l I 3 51 1 27 43 I 13 17 US. Patent Oct. 7,1975

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GLOW PLUG BACKGROUND OF THE INVENTION The background of the invention will be set forth in two parts.

1. Field of the Invention The present invention pertains generally to the field of combustible vapor ignition devices and more particularly to the field of such devices generally known as glow plugs.

2. Description of the Prior Art A glow plug is a means of igniting a combustible vapor, usually an air/fuel mixture, in an engine having a combustion chamber.

For many years, only ignition systems having a coil, one or more spark plugs, points and a self-contained battery were used in relatively small combustion chamber type power plants such as model engines, for example. Because of the problem of timing, the carrying of a heavy ignition battery, coil, etc., and also because the points/coil/spark plug combination generated a consid erable amount of radio frequency energy that interfered with radio systems used to control the various control functions of the vehicle powered by such engines, use of what are commonly referred to as glow plugs became very popular. In fact, at this point in time, the use of ignition-type model engines is virtually nonexistent.

The glow plug was probably first commercially made available in model engines as early as I946. At that time, the engines were simply stripped of their timing points and their spark plug was replaced with a glow plug having a glow element usually consisting of several turns of platinum wire connected between the lower tip of the center electrode and the lower edge of the lower plug cavity. An external battery was temporarily connected between the plugs center electrode and body to cause the platinum wire to glow and thereby ignite the fuel mixture in the engine combustion chamber. Once the engine fired, each subsequent explosion kept the platinum wire glowing to repeat the sequence without the external battery being any longer connected to the plug. In this early stage of development, it was found that the various moving parts of the engine were being more highly stressed than when used in a spark ignition mode, and more engine failures occurred. Eventually, the engines were beefed up to withstand the additional stresses brought on the system by the use of glow plugs. However, as the art progressed to engines having higher and higher compression ratios, it was then found that the incidences of glow plug failures were increasing drastically.

Glow plug failures were generally concentrated in the area of seal failures-that is gases under extremely high pressure present in the lower plug cavity (where the coil is located) were rupturing or deforming the sealing elements in the plug to the extent that allowed the gases to escape from the combustion chamber through the glow plug. In many instances, the center electrode was blown completely out of the plugs body.

It should therefore be evident that a new glow plug that included means for permanently sealing a glow plug even under extremely high compression operation would constitute a significant advancement of the art.

SUMMARY OF THE INVENTION In view of the foregoing factors and conditions characteristic of the prior art, it is a primary object of the present invention to provide a new and improved glow plug for igniting combustible vapors.

Another object of the present invention is to provide a blowout-proof glow plug for ignition applications in reciprocal engines, rotary engines, jet engines, and the like.

Still another object of the present invention is to provide a very reliable glow plug type ignitor having a unique compression seal.

Yet another object of the present invention is to provide an easily-fabricated and economical to manufacture glow plug especially adaptable for use in model engines.

According to one embodiment of the present invention, a glow plug for igniting combustible vapors is provided having an elongated body of electrically conductive material through which an elongated bore extends coaxially with the bodys longitudinal axis. The bore includes an increased diameter portion, the upper extremity of which may be formed by an inwardly extending'crimpedlip portion of the upper end of the plugs body. An elongated center electrode is disposed in and spaced'from the walls of the elongated bore, the center electrode including an upper post portion for connection to a source of electrical potential, an intermediate increased diameter electrode portion disposed in the increased diameter bore portion, and a lower electrode portion to which is attached one end of a glow element, the other end being attached to the lower portion of the plugs body. Insulation material is disposed in the increased diameter bore portion above and below the increased diameter electrode portion for electrically insulating the center electrode from the body. The invention also includes a spring washer disposed about the center electrode and in the increased diameter bore portion to provide a generally constant compression force between the increased diameter electrode portion and the upper and lower walls of the increased diameter bore p'ortionto help prevent fluid under pressure in the lower portion of the elongated bore from flowing about the increased diameter electrode portion to the upper portion of the bore.

In accordance with certain embodiments of the invention, the spring washer may be a Bellville washer and may be disposed either below or above the increased diameter electrode portion. Also, a flat washer may be disposed adjacent and either above or below the spring washer.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood by making reference to the following description taken in conjunction with the accompanying drawing in which like reference characters refer to like elements in the several views.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a partial sectional view of a glow plug, prior to final assembly, constructed in accordance with the present invention;

FIG. 2 illustrates a glow plug in accordance with another embodiment of the invention, after final assemy;

FIG. 3 is a portion of a glow plug constructed in accordance with still another embodiment of the invention, subsequent to final assembly;

FIG. 4 shows a portion, in partial section, of a glow plug constructed in accordance with yet another embodiment of the invention; and

FIG. 5 is an illustration of a portion of a glow plug in accordance with yet a further embodiment of the present invention, prior to final assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS:

Referring now to the drawing and more particularly to FIG. 1, there is shown a glow plug 11 for igniting combustible vapors. The plug 11 includes an elongated body 13 of electrically conductive material such as steel which has an upper body portion 15, a central portion 17 and a threaded lower body portion 19. Generally coaxial with the longitudinal axis of the body 13 and extending therethrough is an elongated bore 21 having an upper portion 23, a lower portion 25 and an intermediate increased diameter bore portion 27. As shown in FIGS. 2-4, the upper circular wall 29 of the increased diameter bore portion 27 is preferably defined by an inwardly extending crimped lip 31 at the end of the upper body portion 15. The plug 11 also includes a center electrode 33 of conductive material such as steel, for example, disposed in but spaced from the elongated bore 21. The center electrode 33 includes an upper post portion 35 preferably having conventional outwardly extending ribs 37 and an increased diameter end 39. The electrode 33 may also include a transition portion 41 leading to a relatively greater increased diameter intermediate portion 43 that is disposed in the increased diameter bore portion 27. Extending below the portion 43 is a lower electrode portion 45 having a lower end 47 to which one end of a conventional glow element 49 is attached by any conventional means such as spot welding, for example. The other end of the glow element, which is usually in the form of a helical coil, is attached to the body 13 at its lower portion 19. The glow element may be fabricated from any suitable material such as platinum or platinum alloy including iridium or rhodium, for example.

The plug 11 further includes electrical insulation material preferably in the form of fiat annular discs or washers 51 disposed about the center electrode 33 on each side of the increased diameter portion 43 to prevent electrical contact between these sides of the electrode portion 43 and the body 13. The insulating washers are preferably limitedly deformable under pressure so as to help provide a gas-tight seal, as will hereinafter be described in greater detail. These washers may be of an asbestos-type material, for example, but other conventional materials exhibiting the desired characteristics may be used. As seen in FIG. 1, an annular spring washer 53, such as a Bellville washer, is disposed about the transition portion 41 of the electrode 33 and between the upper insulating annular discs 51 and a conventional flat washer 55. The concave surface 57 of the spring washer 53 is positioned upwardly so that the outer edge thereof does not cut into the insulation layer and thereby contact the center electrode 33. It will be noted that spacing between the center electrode and the body, the use of insulators 51, and the diameter of the openings in the metal spring and flat washers being greater than the outer diameter of the center electrode,

are all calculated to prevent unwanted electrical contact between the electrode 33 and the body 13 except through the glow element 49.

The glow plug 11 as seen in FIG. 1 is shown prior to a production step of crimping the top end of the upper body portion 15 to form the crimped lip 31 (FIG. 2). This step forces the flat washer 55 to move downwardly and thereby compress the spring washer 53, after the insulating washers 51 are in turn compressed. In its compressed state, the spring washer 53 continues to exert an essentially constant pressure on all of the elements in the increased diameter bore portion 27 which insures a reliable high pressure seal in this area.

The sealed condition of a glow plug which is similar to the plug 11 is illustrated in FIG. 2. In his embodiment, it will be noted that the spring washer 53 in glow plug 61 appears flat. However, the slight amount of curvature that may remain in the washer 53 after being compressed by the formation of the crimped lip 31 is not shown for the sake of simplicity. The only difference between this embodiment and the first embodiment of FIG. 1 is the addition of what is known as an idle-bar 63. The idle-bar is usually a piece of steel attached at its ends to opposite sides of the lower bore portion by any conventional means such as welding, for example.

The idle-bar has been found to be very advantageous in glow plugs for use in model reciprocal engines because it provides more reliable idle speed operation by shielding the glow element 49 from a highly liquid laden incoming charge of air/fuel mixture that could lower the temperature of the element.

It has been found that the spring washer 53 may advantageously be located in the increased diameter bore portion 27 at positions other than that shown in FIGS. 1 and 2. For example, in the embodiment of FIG. 3, the location of the spring washer 53 in the glow plug 71 is above the flat washer 55 so that the crimped lip 31 presses directly on the washer 53. In all other respects, the glow plug 71 is similar in structure and operation to either of the previously described glow plugs.

Referring now to FIG. 4, there is shown glow plug 81 constructed similarly to the previously described plugs but not incorporating a flat washer adjacent the spring washer 53. Thus, the partially-formed crimped lip 31 is shown pressing directly down on the upwardly extending outer edge of the washer 53 which, in turn, bears down on the upper insulating washer 51. Conversely, a spring washer 53 may be located below the increased diameter electrode portion 43 to provide the very advantageous seal-making compressive force between the elements in the increased diameter bore portion 27, as illustrated for the glow plug 91 in FIG. 5.

The glow plugs described above operate in exactly the same manner as conventional glow plugs and no special equipment or procedures are required for their use. Thus, to utilize any of these plugs, the threaded lower body portion 19 is screwed into an appropriate threaded hole communicating with a combustion chamber in an engine, for example. A source of poten- I tial having a magnitude suitable for the glow element being used is then temporarily connected between the upper post portion 35 of the center electrode 33 and the engine frame or the body 13. The glow element 49 will thus become very hotand will ignite a suitable airfuel mixture present in the engines combustion chamber to cause the required explosion. The explosion itself, and those following, will keep the glow element at a very high temperature to continue to ignite a newly introduced air/fuel charge, without the source of potential (usually a battery) being connected to the plug.

Preferably, the increased diameter electrode portion 43 is relatively thick, as shown, but a thinner dimension may be utilized. Also, other means to enclose the various sealing elements in the increased diameter bore portion may be used within the contemplation of the invention. It should therefore be understood that although certain materials, configurations and processes have been described in detail, other materials, configurations and processes having or performing the same or similar characteristics may be utilized. It should further be understood that the glow plug body 13 may be configured to function as the cylinder head of a model engine, thus not limiting the glow plug 11 to a configuration to which it is screwed into a cylinder head of such an engine.

From the foregoing, it should be evident that there has herein been described a highly advantageous, yet simple and economical-to-construct glow plug that has a very increased resistance to blowout of its stem or center electrode even when used in very high compression conditions.

What is claimed is:

l. A glow plug for igniting combustible vapors, comprising:

an elongated body of electrically conductive material and having a longitudinal axis and a longitudinal bore extending through said body coaxial with respect to said axis, said bore including an increased diameter bore portion;

a center electrode disposed in but spaced from the walls of said bore and including an upper post portion extending beyond said bore, an intermediate increased diameter electrode portion disposed in said increased diameter bore portion, and a lower electrode portion;

a glow element attached to said lower electrode portion and to the lower portion of said body;

insulation means including electrical insulation material disposed in said increased diameter bore portion at least above and below said increased diameter electrode portion for electrically insulating said center electrode from said body; and

compression means including a spring washer disposed about but spaced from said center electrode and in said increased diameter bore portion for providing a generally constant compression force between said increased diameter electrode portion and the upper and lower walls of said increased diameter bore portion and permanently preventing gas under pressure located in the lower portion of the bore from passing about the increased diameter electrode portion to the upper portion of the bore, and the upper end of said body adjacent said longitudinal bore includes an inwardly extending crimped lip portion defining the circular upper wall of said increased diameter bore portion.

2. The glow plug according to claim 1, wherein said insulation means includes annular insulating washers disposed about said center electrode at each side of said increased diameter electrode portion.

3. The glow plug according to claim 1, wherein said spring washer is a Bellville spring washer.

4. The glow plug according to claim 1, wherein said spring washer is disposed about said upper post portion of said center electrode.

5. The glow plug according to claim 1, wherein said spring washer is disposed about said lower electrode portion of said center electrode.

6. The glow plug according to claim 1, also comprising a flat washer juxtaposed said spring washer.

7. The glow plug according to claim 6, wherein said flat washer is disposed between the upper wall of said increased diameter bore portion and said spring washer.

8. The glow plug according to claim 6, wherein said flat washer is disposed between said increased diameter electrode portion and said spring washer.

9. The glow plug according to claim 1, also comprising an electrically conductive idle-bar extending across said longitudinal bore at the lower end of said body.

10. The glow plug according to claim 9, wherein said idle-bar is bowed outwardly at its center. 

1. A glow plug for igniting combustible vapors, comprising: an elongated body of electrically conductive material and having a longitudinal axis and a longitudinal bore extending through said body coaxial with respect to said axis, said bore including an increased diameter bore portion; a center electrode disposed in but spaced from the walls of said bore and including an upper post portion extending beyond said bore, an intermediate increased diameter electrode portion disposed in said increased diameter bore portion, and a lower electrode portion; a glow element attached to said lower electrode portion and to the lower portion of said body; insulation means including electrical insulation material disposed in said increased diameter bore portion at least above and below said increased diameter electrode portion for electrically insulating said center electrode from said body; and compression means including a spring washer disposed about but spaced from said center electrode and in said increased diameter bore portion for providing a generally constant compression force between said increased diameter electrode portion and the upper and lower walls of said increased diameter bore portion and permanently preventing gas under pressure located in the lower portion of the bore from passing about the increased diameter electrode portion to the upper portion of the bore, and the upper end of said body adjacent said longitudinal bore includes an inwardly extending crimped lip portion defining the circular upper wall of said increased diameter bore portion.
 2. The glow plug according to claim 1, wherein said insulation means includes annular insulating washers disposed about said center electrode at each side of said increased diameter electrode portion.
 3. The glow plug according to claim 1, wherein said spring washer is a Bellville spring washer.
 4. The glow plug according to claim 1, wherein said spring washer is disposed about said upper post portion of said center electrode.
 5. The glow plug according to claim 1, wherein said spring washer is disposed about said lower electrode portion of said center electrode.
 6. The glow plug according to claim 1, also comprising a flat washer juxtaposed said spring washer.
 7. The glow plug according to claim 6, wherein said flat washer is disposed between the upper wall of said increased diameter bore portion and said spring washer.
 8. The glow plug according to claim 6, wherein said flat washer is disposed between said increased diameter electrode portion and said spring washer.
 9. The glow plug according to claim 1, also comprising an electrically conductive idle-bar extending across said longitudinal bore at the lower end of said body.
 10. The glow plug according to claim 9, wherein said idle-bar is bowed outwardly at its center. 